Hydraulic load carrier

ABSTRACT

A hydraulic load carrier having a hydraulic powered lift platform, forks and horizontal drive includes variable proportional flow valves to variably control the flow of hydraulic power fluid to the lift platform, forks and drive to selectively and independently control the speed of each of these components. Velocity and acceleration means may be provided in one or more of the hydraulic circuits to limit the maximum velocity and acceleration, respectively, of the components and to prevent uncontrolled free fall of the lift platform.

United States Patent Redelman 154] HYDRAULIC LOAD CARRIER [72] lnventor: Paul E. Redelman, South Holland,

Ill.

[73] Assignee: Intel-lake Steel Corporation [22] Filed: April 21, 1970 [21] Appl. No.: 30,452

[52] US. Cl ..2l4/730, 91/411 [51] Int. Cl. ..B66f 9/14 [58] Field of Search .....214/l6.42, 730; 91/411, 420, 91/444 [56] References Cited UNITED STATES PATENTS 2,675,134 4/1954 Becker ..2l4/l6.42

3,216,599 11/1965 Hopfeld 2,648,346 8/1953 Deardorff et al....

- [451 Dec. 5, 1972 3/1964 Vivier ..9l/42O 6/1939 Strawn ..60/52R Primary Examiner-Gerald M. Forlenza Assistant Examiner-Lawrence J. Oresky Attorney-Molinare, Alegretti, Newitt & Witcoff [57] ABSTRACT A hydraulic load carrier having a hydraulic powered lift platform, forks and horizontal drive includes variable proportional flow valves to variably control the flow of hydraulic power fluid to the lift platform, forks and drive to selectively and independently control the speed of each of these components. Velocity and acceleration means may be provided in one or more of the hydraulic circuits to limit the maximum velocity and acceleration, respectively, of the components and to prevent uncontrolled free fall of the lift platform.

13 Claims, 2 Drawing Figures L J POWER su p CIRCUIT PATENTEDBEI: 5:912

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HYDRAULIC LOAD CARRIER BACKGROUND AND SUMMARY OF THE INVENTION 1 storage installation.

Load carriers have been provided in the past for horizontally moving articles into and out of storage installations, vertically positioning the articles in alignment with vertically spaced bins by way of a lift platform, and extendible forks carried upon the lift platform for transferring articles between the bins and the lift platform. In such load carriers, it is desirable that the speed at which the load carrier is horizontally moved, as well as the speed at which the lift platform is elevated or lowered, be capable of wide variation and be easily and smoothly controlled over the wide range of speeds. For example,it is desirable that the speed of the load carrier in the horizontal direction be variable over a wide range between a relatively high speed for operation between the pickup or delivery station and the bin and a substantially slower inching speed adjacent the station or bin to insure accurate and exact positioning of the load carrier and its lift platform.

The'hydraulic load carrier and control arrangement incorporating the principles of the invention is capable of operating smoothly over a wide range of infinitely variable speeds in both the horizontal and verticaL'The load carrier incorporating the principles of the invention is capable of handling an extensive range of load weights, since the load carrier may be operated at a slow speed with high mechanical advantage when handling loads of substantial weight and at a higher speed when handling light loads. In the load carrier of the invention, the likelihood of inertial damage to the articles being handled is substantially reduced. In the load carrier and control arrangement of the invention, control of three dimensional movement of the articles is made possible by the use of only two manual controls. Moreover, both the horizontal movement of the load carrier, as well as the vertical movement of the lift platform may be independently varied over a wide range of speeds. In the load carrier of the invention, one or both maximum velocity and/or acceleration control may be readily provided. In addition, the possibility of free fall of the lift platform in the load carrier incorporating the principles of the invention is substantially eliminated.

In a principal aspect of the invention, a load carrier includes a lift platform, conveying means and drive means for effecting movement of articles vertically, transverse of the load carrier and for driving the load carrier horizontally, respectively. Fluid motor means drives the lift platform, conveying means and drive means and variable hydraulic valve means selectively communicates each of the fluid motor means with a source of hydraulic fluid to selectively and independently vary the speed of the fluid motor means.

These and other objects, features and advantages of the present invention will be more clearly understood through a consideration of the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS In the course of this description, reference will be frequently made to the attached drawing in which:

FIG. 1 is an isometric view of a preferred embodiment of load carrier and storage installation which incorporates the principles of the invention; and

FIG. 2 is a schematic view of a preferred embodiment of hydraulic control circuit of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1, a load carrier and storage installation is shown for the storage and retrieval of articles. The storage installation, generally 10, comprises a plurality of upstanding racks 11 and 11 which form a plurality of horizontally and vertically spaced bins 12 for the storage of articles. Each series of racks 11 and 11' are spaced from each other so as to provide an aisle l3 therebetween. The storage bins may be formed by way of vertically spaced angles 14 or the like upon which palletized articles, for example P, may be set. An overhead guide rail 15 is mounted adjacent the top of the racks in the overhead of the aisle l3 and the load carrier, indicated generally as 16, is moveable along the guide rail back and forth along the floor of the aisle 13. Additional guide rails (not shown) may be mounted to the racks adjacent the bottom of the load carrier for preventing undesirable lateral movement of the latter during operation,if necessary.

The load carrier 16 preferably comprises a pair of upstanding masts 17 and 17 extending between the overhead rail 15 and the aisle floor and includes a horizontal drive means which powers one or more of the wheels 18 of the load carrier so as to effect horizon tal movement of the entire load carrier back and forth along the aisle. A lift platform 19 is mounted between the masts 17 and 17 and is elevatable by way of a vertical drive means and hoist chain arrangement between a vertical position adjacent the overhead rail 15 to a position adjacent the bottom of the load carrier. A pair of extendible forks 20 are mounted on the horizontal bed of the lift platform 19 and are telescopically extendible transversely to either side of the lift platform by fork drive means so as to position and remove articles in or from the individual bins 12. An operator cage 21 may also becarried as part of the lift platform 19 in which operating personnel may stand while operating the load carrier. The cage 21 is preferably carried for movement with the lift platform.

Thereby it will be seen that the load carrier is capable of manipulating a given article in any one of three dimensions. Horizontal movement of the load carrier 16 back and forth along the aisle 13 will effect horizontal movement of the article between a pickup or delivery station (not shown) and the bins. Elevation of the lift platform 19 will effect vertical movement of the article. An extension or retraction of the telescopic forks 20 will effect movement of the article transverse to the load carrier and lift platform into and out of the bins.

Each of the load carrier horizontal drive means, the lift platform drive means, and the fork drive means is preferably powered by way of hydraulic fluid. A preferred embodiment of hydraulic circuit is shown in FIG. 2 and will now be described.

In general, the overall hydraulic circuit includes four sub-circuits, including a power supply circuit 22, a vertical circuit 23, a fork circuit 24 and a horizontal drive circuit 25.

The power supply circuit 22 includes a suitable hydraulic fluid reservoir 26 from which hydraulic fluid is pumped to the respective drive means and returned thereto through a return line. Fluid is drawn from the reservoir 26 by a pump 28, which is preferably a pressure compensated variable volume pump which is driven by an electric motor 30. The fluid is delivered by the pump under pressure to a hydraulic supply line 32. Filters 34 and 34' may be positioned in the intake and discharge lines of the pump 28 to insure that the fluid which is delivered to the respective drive means is clean and free of sediment and other foreign matter. In addition, a pressure gage 36 may be carried by the supply line 32 to indicate the pressure therein.

From the supply line 32 the pressurized power fluid is delivered by way of hydraulic conduits 38, 39 and 40 to suitable power control means which preferably take the form of hydraulic proportional control valves 42, 43 and 44 in each of the vertical circuit 23, the fork circuit 24 and the horizontal drive circuit 25, respectively. in general, the proportional control valves 42, 43 and 44 are constructed to delivera varying amount of pressurized hydraulic fluid from conduits 38, 39 and 40 to the drive means of each circuit and return the fluid therefrom. The degree of opening and closing of the control valves may be varied and is effected by way of an operating electrical force motor 46, 47 and 48, whereby each valve is capable of delivering hydraulic fluid which is selectively variable over a wide range of flow rates in order to operate the different drive means at a wide variety of speeds. The detailed construction of the proportional control valves 42, 43 and 44 does not form a part of the subject matter of our invention and numerous valves of various constructions are available which could be employed satisfactorily. For this reason, the construction of the control valves will not be set forth in detail herein.

The proportional control valve 42 and its force motor 46 of the vertical circuit 23 is preferably operated by way of a manual operating handle 50 which manipulates a rheostat in an electrical control circuit 52 which is shown in box form in FIG. 2. A suitable electrical circuit which may be employed in circuit 52, as well as circuits 52A and 528 which will later be mentioned is shown in Gerald M. Kwaitkowskis and my copending U.S. application, Ser. No.

30,453, now U.S. Pat. No. 3,628,678 patented Dec. 2l i971 filed on the same date as this application. Even though the disclosure of Ser. No. 30,452 is found in U.S. Pat. No. 3,628,678, the claimed invention of the Ser. No. 30,452 application is the sole invention of Redelman. The control circuit 52 operates to variably drive the motor 46 of control valve 42 so as to either close the control valve or variably open the valve. The valve 42 and its motor are constructed so as to be reversible, whereby the drive means of the vertical circuit may be operated in either direction. A plurality of conduits are connected to the control valve 42, including the hydraulic conduit 38, a return conduit 54, a conduit 55 which extends between the control valve and the drive means 56 of the vertical circuit, and a conduit 58 which extends between the control valve and the pilot section 59 of a directional flow valve 60. A check valve 62 is located in conduit 55. The check valve 62 allows flow only in a direction from valve 42 to the drive means 56. A bypass 64 bypasses the check valve 62 and the directional flow valve 60 is positioned in the bypass.

The directional flow valve 60 provides a path for return of the hydraulic fluid to the reservoir 26. Valve 60 is constructed such that when hydraulic fluid at system pressure is delivered through conduit 58 to the pilot section 59 of the valve, the valve will be'deactuated and, in effect, open for substantially unrestricted flow in the direction indicated by the arrow. However, when conduit 58 is closed to the pilot section, the valve becomes loaded so as to close. The operation of valve 60 will be described in more detail when describing the operation of the vertical circuit 23. The specific construction of valve 60 will not be set forth herein in detail, a suitable variety of valves of varied construction being within the selection of one skilled in the art once he has considered the teachings of the invention.

The vertical circuit also includes a variable resistance orifice 66 which is adjusted so as to have a constant pressure drop thereacross for a given system. The orifice 66 is positioned between the check valve 62 and the drive means 56. The variable orifice 66 acts to control the maximum velocity at which the drive means 56 may be operated, nd also since the variable orifice is positioned between the control valve 42 and the drive means 56, it prevents accidental free fall of the lift platform in the event of a power failure by limiting the outflow of hydraulic fluid from the drive means. If it is desired to increase or decrease the maximum system velocity, the orifice may be simply adjusted without changing any of the other components of the system. Thereby, a given system is rendered capable of use under a wide variety of conditions simply by varying the orifice 66.

The lift platform drive means 56 comprises a cylinder 68 and piston 70. Conduit 55 communicates with the upperside of the piston 70 and the piston rod 72 of the piston is connected to the lift platform 19 by way of suitable hoist chains or the like 74 and sprockets 75 shown schematically in FIG. 2.

In operation, when the piston 70 is driven downward as viewed in FIG. 2 by the hydraulic fluid, the hoist chains 74 are tensioned and the platform 19 is hoisted upward. When it is desired to lower the lift platform 19, the weight of the platform and any article positioned upon the platform, is exerted by way of the hoist chains 74 upon the piston rod 72 to pull the piston 70 upward as viewed in FIG. 2, thereby discharging the fluid from above the cylinder back through conduit 55.

A gland seal drain conduit 76 may be provided to collect any hydraulic fluid which may escape from around the piston rod 72. Such fluid may be collected in an individual reservoir 77, as shown, or returned directly to reservoir 26.

The vertical operation of the hydraulic circuit will now be described.

When it is desired to elevate the lift platform 19, the operating handle 50 is moved in one direction, for example to 50 as shown in FIG. 2. Movement of the operating handle from its offcenter position will effect operation of the control valve 42 by way of the electrical control circuit 52 and motor 46 so as to at least partially open the control valve. The degree to which handle 50 may be moved may be varied between any one of a number of positions so as to selectively vary the amount by which the valve is opened.

Hydraulic fluid, supplied under pressure from pump 28 to conduit 32, passes through conduit 38 to the control valve. Opening of the valve 42 to elevate the lift platform now connects conduit 38 with conduit 55 and conduit 58 with the return conduit 54. Pressurized hydraulic fluid is thereby delivered through the conduit 55 via check valve 62 to variable orifice 66 and then into cylinder 68 to the top of piston 70, driving the piston downward and hoisting the lift platform 19 by way of hoist chain 74. Since conduit 58 is in communication with the return conduit 54, the pilot section 59 of the directional flow valve 60 is vented to substantially atmospheric pressure which obtains in reservoir 26, shutting the flow valve 60.

Once the piston and lift platform have been set into motion, the maximum velocity at which the piston and its platform will move is determined by the variable orifice 66, since the variable orifice setting is adjusted so as to limit maximum flow rate therethrough.

When the platform has been elevated to its desired height, the handle 50 is again centered. In such position, the valve 42 is closed isolating conduits 38 and 54 from conduits 55 and 58 to trap the fluid and maintain the platform at its desired elevation.

If it is now desired to lower the lift platform 19, the operating handle 50 is moved from its dead center position in the opposite direction, for example to 50 as shown in FIG. 2. Movement of the operating handle may again be to any one of a number of positions so as to variably operate control valve 42 by way of the electrical control circuit 52 and motor 46. In lowering the lift platform, the control valve 42, is lined up so as to communicate conduit 38 with conduit 58 and conduit 55 with the return conduit 54.

Pressurized hydraulic fluid is now supplied to the pilot section 59 of the flow valve 60 to open the flow valve for substantially unrestricted flow in the direction indicated by the arrow in FIG. 2. The weight of the lift platform 19 now pulls upward upon the piston 72 by way of the hoist chain 74, to move the piston 70 upward in the cylinder. As the piston moves upward, the hydraulic liquid above the piston is displaced from the cylinder back through the orifice 66, through the bypass 64 and now open flow valve 60 around the check valve 62, back to conduit 55, through the control valve 42, through the return conduit 54 and back to the reservoir 26.

It should be noted that the variable opening of the control valve 42 normally acts to limit and variably control the rate of descent of the lift platform by controlling the rate at which the liquid is returned from the cylinder. If for any reason, for example due to power failure of the electrical control circuit 52, the control valve 42 is accidentally fully opened and cannot be shut, a dangerous rate of descent of the lift platform 19 will be prevented by the action of the orifice 66 which will effectively set the maximum rate of return flow which may pass through the conduit 55.

Now referring to the fork circuit 24, in addition to supply conduit 39 which connects the pump 28 with control valve 43, a return conduit 78 is also provided which connects the valve 43 with the reservoir 26. A variable orifice 80, similar to orifice 66, is provided in the supply conduit 39 before the control valve. The force motor 47 of the control valve 43 is controlled by way of a four-way operating handle 82, the operating handle being moveable in a first linear direction, for example between positions 82' and 82" in FIG. 2. to effect operation of an electrical control circuit 52A and the force motor 47 of control valve 43 and in a second linear direction, for example between positions 82" and 82"" in FIG. 2, to effect operation of an electrical control circuit 528 and the force motor 48 of the control valve 44 of the horizontal drive circuit 25. Thus, only two operating handles 50 and 82 need be provided in order to control the three control circuits 52, 52A and 52B, operating handle 50 controlling the vertical circuit 23 and operating handle 82 controlling both the fork and horizontal drive circuits 24 and 25.

A pair of hydraulic conduits is provided in the fork circuit 24, one of the conduits 83 communicating between the control valve 43 and one side of a reversible hydraulic motor 86 and the other conduit 84 communicating between the hydraulic motor 86 and the control valve 43. Check valves 87 and 88 are located in each of the conduits 83 and 84 and provide for flowonly from the valve 43 to the motor 86. A cross connect conduit 90 is also provided which extends between the conduits 83 and 84 before the check valves 87 and 88 and a pair of directional flow valves 91 and 92 are each located in bypasses'94 and 95. The bypasses communicate at one end with the conduits 83 and 84 between the check valves 87 and 88 and the motor 86 and at the other end with conduit 90. A pair of check valves 97 and 98 are each located in conduit 90 between one end of the bypasses 94 and and conduits 83 and 84 providing for flow only from the bypasses to the respective conduits, as shown in FIG. 2.

In order to pressurize and vent the pilot sections 100 and 101 of the flow valves 91 and 92 respectively to enable operation of the flow valves, a conduit 102 is connected between pilot section 101 of valve 92 and conduit 83 before check valve 87 and another conduit 103 is connected between pilot section 100 of valve 91 and conduit 84 before check valve 88.

The operation of the fork circuit 24 will now be described.

If it is desired to extend the forks 20 from their centered position on the lift platform 19, the operating handle 82 is moved toward one of the positions 82' and 82" to on? of any one of a number of positions so as to effect a variable opening of the control valve 43 by way of the electrical control circuit 52A and force motor 47. For example, movement of the handle in one direction will operate the valve 43 so as to communicate the hydraulic supply conduit 39 with conduit 83 and the conduit 84 with the return conduit 78. Thus, hydraulic fluid under pressure is delivered through the variable orifice 80, through conduit 39 to the control valve 43, to conduit 83, through the check valve 87 and is delivered to the hydraulic motor 86 to drive the motor. The pressure in conduit 83 is also supplied to the pilot section 101 of the flow valve 92 through conduit 102 to open the valve and allow return of the exhaust fluid around check valve 88. Thus, the exhaust fluid from the hydraulic motor 86 flows from the motor to conduit 84, through the bypass 95 and now open valve 92 to conduit 90, through check valve 98 back to the conduit 84, through the control valve 43 and through the return line 78 to the reservoir 26. Since the exhaust fluid is at a substantially lower pressure than the supply fluid in conduit 83, no flow will occur across check valve 97 to the conduit 83.

If it is now desired to move the forks in a direction opposite to that previously described, for example if it is desired to return the forks from the extended position or extend the forks to the opposite side of the platform, the operating handle is moved in the opposite direction, thereby effecting a variable opening of the control valve 43 opposite to that previously described. More specifically, movement of the control valve 43 in the opposite direction will communicate the hydraulic supply conduit 39 with conduit 84 and conduit 83 with the return conduit 78. Pressurized hydraulic fluid will now flow through the variable orifice 80, supply conduit 39, the control valve 43, conduit 84 and check valve 88 into he motor 86. The pressure in conduit 84 will be transmitted to the pilot section 100 of the flow valve 91 to open the valve. Thus, the exhaustfrom the motor 86 will flow from the motor through conduit 83, through bypass 94 and the now open valve 91, through check valve 97, back to the conduit 83, through the control valve and through the return line 78 to the reservoir 26. i

It will be noted that, without regard to the direction in which the motor is operated, the variable orifice 80 will act to limit the maximum velocity of the motor 86 as previously described with respect to the variable orifice 66 in the vertical circuit 23, since the conduit 39 is always a supply conduit.

Additionally, each of the flow valves 91 and 92 will operate to limit the maximum acceleration rate of the motor 86 no matter which way the motor is being operated. in operation, the flow valves are normally shut when their respective pilot sections are not pressurized, but will open in the event that the pressure in their conduit 83 or 84 exceeds a certain value. Thereby, if the motor 86, for example, is to be started in one direction and the peak' pressure in conduit 83 or 84 which is necessary to overcome the inertia of the motor exceeds the setting of the closed valve 91 or 92, the valve 91 or 92 will dump a portion of the fluid to the return line, thus acting to limit the peak" pressure and, in turn, control maximum acceleration.

The components of the horizontal drive circuit are substantially similar to the components previously described in the fork circuit 24, except for possible variation in size or capacity between the circuits. Accordingly, in describing the construction and operation of the horizontal drive circuit 25, the same reference numerals employed in the identity of the components of the fork circuit will be used, except that they will be primed The horizontal drive circuit includes a supply conduit 40 which communicates between the pump 28 and the control valve 44 and a return conduit 78' communicating between the control valve 44 and the reservoir 26. A variable orifice 80' is positioned in the conduit 40 before the control valve 44. A pair of conduits 83 and 84' are provided, one of which communicates between the control valve 44 and the hydraulic motor 86' and other of which communicates between the motor and the control valve. Each of the conduits 83' and 84' includes check valves 87 and 88' and a pair of flow valves 91' and 92' are positioned in bypasses 94 and 95 which communicate with conduits 83 and 84 at one end and with cross conduit at the other end. A pair of check valves 97' and 98 are provided between the ends'of the bypasses 94 and and the conduit 83' and 84 and provide for flow in one direction only as indicated in FIG. 2. Also, a pair of conduits 102' and 103' each communicate between the conduits 83 and 84' and the pilot sections 100' and 101' ofvalves 91' and 92'.

Since the operation of the horizontal hydraulic drive circuit 25 is substantially the same as previously described with respect to the fork circuit 24, the operation will not be set forth herein in detail. In order to provide hydraulic fluid to motor 86', however, the operating handle 82 is moved in the other linear direction between positions 82" and 82" as shown in FIG. 2, to thereby variably actuate force motor 48 rather than 47.

lt will be understood that the embodiment of the present invention which has been described is merely illustrative of an application of the principles of the invention. Numerous modifications may be made by those skilledin the art without departing from the true spirit and scope of the invention.

What is claimed is:

1. In a load carrier for storing and retrieving articles in a storage installation, which includes a lift platform for effecting movement of the articles vertically, conveying means for effecting movement of the articles transverse of the load carrier and drive means for driving the load carrier in the horizontal, a fluid control arrangement comprising in combination therewith;

a fluid pressure source,

first, second and third fluid control circuits communicating with said fluid pressure source, said first fluid control circuit including first fluid motor means driving said lift platform for elevating the articles in the vertical and first proportional valve means for variably controlling the amount of flow of fluid between said fluid pressure source and said first fluid motor means to controllably vary the speed of said first fluid motor means over a wide range of predetermined speeds,

said second fluid control circuit including second fluid motor means driving said conveying means for moving the articles transverse of the load carrier and second proportional valve means for variably controlling the amount of flow of fluid between said fluid pressure source and said second fluid motor means to controllably vary the speed of said second fluid motor means over a wide range of predetermined speeds,

said third fluid control circuit including third motor means driving said drive means for moving the articles in the horizontal direction and third proportional valve means for variably controlling the amount of flow of fluid between said fluid pressure source and said third fluid motor means to controllably vary the speed of said third fluid motor means over a wide range of predetermined speeds velocity limiting means in at least some of said circuits independent of said proportional valve means of said some of said circuits for limiting the maximum velocity of at least some of said fluid motor means by restricting the flow of fluid between said motor means and said pressure source to an amount less than the maximum of said amount of flow of fluid otherwise permitted by said some of said circuits.

2. The combination of claim 1 wherein said fluid is hydraulic.

3. The combination of claim 1 including acceleration limiting means in at least some of said circuits for limiting the maximum acceleration of at least some of said fluid motor means.

4. The combination of claim 1 wherein said velocity limiting means comprises a variable orifice.

5. The combination of claim 1 wherein said first fluid motor means comprises a fluid cylinder and piston therein operatively mounted to the article carrying lift platform of the load carrier to elevate said platform,

a conduit communicating between one side of said piston and said first proportional valve means,

said proportional valve means being selectively operable to deliver pressurized fluid from said fluid source to said conduit and said one side of said piston for elevating said lift platform and to return fluid from said conduit and said one sideof said piston to said fluid source by the weight of said lift platform to lower the platform.

6. The combination of claim 5 including velocity limiting means in said conduit for limiting the maximum velocity at which said piston moves, said velocity limiting means being positioned between said piston and said proportional valve means.

7. The combination of claim 1 wherein said second and third circuits each comprise first and second conduits communicating between said second and third fluid motor means and said second and third proportional valve means,

check means in each of said conduits permitting flow only from said proportional valve means to said motor means,

first and second bypass means in each of said first and second conduits bypassing their respective check means,

said second and third proportional valve means being selectively operable to deliver fluid from said pressure source to said first conduits through said check means in said first conduits and return fluid to said pressure source from said second conduits through said bypass means in said second conduits to drive said second and third fluid motor means in one direction and also to deliver fluid from said pressure source to said second conduits through said check means in said second conduits and return fluid to said pressure source from said first conduits through said bypass means in said first conduits to drive said second and third motor means in the opposite direction.

8. The combination of claim 7 including acceleration limiting'means in each of the bypass means of said first and second conduits.

9. The combination of claim 7 including velocity limiting means between said second and third proportional valve means and said pressure source for limiting the maximum velocity of said second and third fluid motor means.

10. In the combination of claim 1 including velocity limiting means in each of said circuits limiting the maximum velocity of said first, second and third fluid motor means, respectively, said velocity limiting means in said first control circuit restricting the flow of fluid from said first fluid motor means in the event said first circuit fails.

11. In the combination of claim 1 wherein said first fluid control circuit is operable to raise and lower said lift platform when said third fluid motor means is driving said drive means.

12. A load carrier for manipulating articles in a storage installation, said load carrier including at least one drive means for effecting movement of at least one of the following: the articles in a vertical direction, the articles in a horizontal direction and the load carrier in a horizontal direction, the improvement in said load carrier comprising:

a fluid pressure source,

fluid control circuit means communicating with said fluid pressure source, said drive means including fluid motor means in said fluid control circuit means for effecting said movement,

proportional valve means in said fluid control circuit means for variably controlling the amount of flow of fluid between said fluid pressure source and said fluid motor means to controllably vary the speed of said fluid motor means over a wide range of predetermined speeds, and

velocity limiting means in said fluid control circuit means independent of said proportional valve means for limiting the maximum velocity of said fluid motor means by restricting the flow of fluid between said motor means and said pressure source to an amount less than the maximum of said amount of flow of fluid otherwise permitted by said fluid control circuit means.

13. The load carrier of claim 12 wherein said velocity limiting means comprises a variable orifice. 

1. In a load carrier for storing and retrieving articles in a storage installation, which includes a lift platform for effecting movement of the articles vertically, conveying means for effecting movement of the articles transverse of the load carrier and drive means for driving the load carrier in the horizontal, a fluid control arrangement comprising in combination therewith; a fluid pressure source, first, second and third fluid control circuits communicating with said fluid pressure source, said first fluid control circuit including first fluid motor means driving said lift platform for elevating the articles in the vertical and first proportional valve means for variably controlling the amount of flow of fluid between said fluid pressure source and said first fluid motor means to controllably vary the speed of said first fluid motor means over a wide range of predetermined speeds, said second fluid control circuit including second fluid motor means driving said conveying means for moving the articles transverse of the load carrier and second proportional valve means for variably controlling the amount of flow of fluid between said fluid pressure source and said second fluid motor means to controllably vary the speed of said second fluid motor means over a wide range of predetermined speeds, said third fluid control circuit including third motor means driving said drive means for moving the articles in the horizontal direction and third proportional valve means for variably controlling the Amount of flow of fluid between said fluid pressure source and said third fluid motor means to controllably vary the speed of said third fluid motor means over a wide range of predetermined speeds velocity limiting means in at least some of said circuits independent of said proportional valve means of said some of said circuits for limiting the maximum velocity of at least some of said fluid motor means by restricting the flow of fluid between said motor means and said pressure source to an amount less than the maximum of said amount of flow of fluid otherwise permitted by said some of said circuits.
 2. The combination of claim 1 wherein said fluid is hydraulic.
 3. The combination of claim 1 including acceleration limiting means in at least some of said circuits for limiting the maximum acceleration of at least some of said fluid motor means.
 4. The combination of claim 1 wherein said velocity limiting means comprises a variable orifice.
 5. The combination of claim 1 wherein said first fluid motor means comprises a fluid cylinder and piston therein operatively mounted to the article carrying lift platform of the load carrier to elevate said platform, a conduit communicating between one side of said piston and said first proportional valve means, said proportional valve means being selectively operable to deliver pressurized fluid from said fluid source to said conduit and said one side of said piston for elevating said lift platform and to return fluid from said conduit and said one side of said piston to said fluid source by the weight of said lift platform to lower the platform.
 6. The combination of claim 5 including velocity limiting means in said conduit for limiting the maximum velocity at which said piston moves, said velocity limiting means being positioned between said piston and said proportional valve means.
 7. The combination of claim 1 wherein said second and third circuits each comprise first and second conduits communicating between said second and third fluid motor means and said second and third proportional valve means, check means in each of said conduits permitting flow only from said proportional valve means to said motor means, first and second bypass means in each of said first and second conduits bypassing their respective check means, said second and third proportional valve means being selectively operable to deliver fluid from said pressure source to said first conduits through said check means in said first conduits and return fluid to said pressure source from said second conduits through said bypass means in said second conduits to drive said second and third fluid motor means in one direction and also to deliver fluid from said pressure source to said second conduits through said check means in said second conduits and return fluid to said pressure source from said first conduits through said bypass means in said first conduits to drive said second and third motor means in the opposite direction.
 8. The combination of claim 7 including acceleration limiting means in each of the bypass means of said first and second conduits.
 9. The combination of claim 7 including velocity limiting means between said second and third proportional valve means and said pressure source for limiting the maximum velocity of said second and third fluid motor means.
 10. In the combination of claim 1 including velocity limiting means in each of said circuits limiting the maximum velocity of said first, second and third fluid motor means, respectively, said velocity limiting means in said first control circuit restricting the flow of fluid from said first fluid motor means in the event said first circuit fails.
 11. In the combination of claim 1 wherein said first fluid control circuit is operable to raise and lower said lift platform when said third fluid motor means is driving said drive means.
 12. A load carrier for manipulating articles in a storage installation, said load carrier incLuding at least one drive means for effecting movement of at least one of the following: the articles in a vertical direction, the articles in a horizontal direction and the load carrier in a horizontal direction, the improvement in said load carrier comprising: a fluid pressure source, fluid control circuit means communicating with said fluid pressure source, said drive means including fluid motor means in said fluid control circuit means for effecting said movement, proportional valve means in said fluid control circuit means for variably controlling the amount of flow of fluid between said fluid pressure source and said fluid motor means to controllably vary the speed of said fluid motor means over a wide range of predetermined speeds, and velocity limiting means in said fluid control circuit means independent of said proportional valve means for limiting the maximum velocity of said fluid motor means by restricting the flow of fluid between said motor means and said pressure source to an amount less than the maximum of said amount of flow of fluid otherwise permitted by said fluid control circuit means.
 13. The load carrier of claim 12 wherein said velocity limiting means comprises a variable orifice. 